Preparation And Performance Of Electrocatalysts Of Water Splitting Based On Transition Metal Sulfides Heterojunction Nanoarrays

With the continuous development of industry and life in human society,the demand for energy is also increasing.At the same time,in order to achieve the strategic goal of emission peak and carbon neutrality as soon as possible,hydrogen energy,an efficient clean energy,has been favored by the majority of researchers.Hydrogen production technology by electrochemical water splitting has the advantages of environmental protection,simple process and low cost,which is expected to become the main method of industrial hydrogen production.In the process of electrochemical water splitting,Hydrogen Evolution Reaction（HER）and Oxygen Evolution Reaction（OER）occur respectively at the cathode and anode.Under standard conditions,the thermodynamic potential required to drive this reaction is 1.23V.However,due to its slow dynamic process in actual production,the actual voltage required is much higher than 1.23V.Noble metal catalyst has excellent catalytic performance,but its reserves are scarce and the price is high,which can not be used for large-scale production.Therefore,to exploit efficient and cheap non-noble metal catalysts is the key to solve the problem of hydrogen production by electrochemical water splitting.In this paper,Co@Co S and Ni₃S₂@Cu（OH）₂heterogeneous electrocatalysts were prepared with transition metal sulfides as the research direction.In order to show that transition metal sulfides have good catalytic performance in both HER and OER catalysis,the two heterostructures prepared were used as HER and OER catalysts respectively.Co S nanowires array were prepared on carbon cloth by hydrothermal sulfidation method,and Co was loaded onto the nanowire by electrodeposition method to form Co@Co S heterostructure.The sample has clear phase composition,uniformly distributed morphology and structure,and the formation of heterogeneous structure is helpful to improve its catalytic performance,and the catalytic performance of heterogeneous catalysts is improved compared with that of single catalysts.When the catalyst was tested for HER catalytic performance in 1 M KOH solution,the overpotential required to drive the current density of 20 m A cm^-2is only 225 m V,and the Tafel slope was 59.7 m V dec^-1.Subsequently,the stability of the catalyst was tested at 10,20 and 50 m A cm^-2for totally 15 h.After the test,the catalytic performance and phase composition of the sample did not change significantly.The results showed that HER electrocatalyst with excellent catalytic performance was synthesized by hydrothermal sulfidation and electrodeposition.Cu（OH）₂nanowires array structure was prepared on copper foam substrate by anodic oxidation method,and then Ni₃S₂was loaded onto the nanowires by electrodeposition method to form Ni₃S₂@Cu（OH）₂heterogeneous structure,and the catalytic performance of heterogeneous catalysts is improved compared with that of single catalysts.When the catalyst was tested for OER catalytic performance in 1 M KOH solution,the overpotential required to drive the current density of 100 m A cm^-2was only 335 m V,with a Tafel slope of 47.5 m V dec^-1.After the stability test of the sample at 10,20 and 50 m A cm^-2for 15 h,it was found that the phase composition and morphology of the sample did not change significantly,and the catalytic activity did not decrease significantly.It follows that an efficient and stable OER electrocatalyst was synthesized by anodic oxidation and electrodeposition.